Toward Optimization of a Novel Trileaflet Polymeric Prosthetic Heart Valve via Device Thrombogenicity Emulation

Abstract

Aortic stenosis the is most prevalent and life threatening form of valvular heart disease. It is primarily treated via open-heart surgical valve replacement with either a tissue or mechanical prosthetic heart valve (PHV), each prone to degradation and thrombosis, respectively. Polymeric PHVs may be optimized to eliminate these complications, and they may be more suitable for the new transcatheter aortic valve replacement (TAVR) procedure and in devices like the Total Artificial Heart. However, the development of polymer PHVs has been hampered by persistent in vivo calcification, degradation, and thrombosis. To address these issues, we have developed a novel surgically implantable polymer PHV comprised of a new thermoset polyolefin called xSIBS, in which key parameters were optimized for superior functionality via our Device Thrombogenicity Emulation (DTE) methodology. In this parametric study, we compared our homogeneous optimized polymer PHV to a prior composite polymer PHV and to a benchmark tissue valve. Our results show significantly improved hemodynamics and reduced thrombogenicity in the optimized polymer PHV compared to the other valves. These results indicate that our new design may not require anticoagulants and may be more durable than its predecessor, and validates the improvement, towards optimization, of this novel polymeric PHV design.

Hemodynamic and thrombogenic analysis of a trileaflet polymeric valve using a fluid–structure interaction approach

“…Assuming the valve works well within the lower values of this range during physiologic cardiac cycles, a linear elastic material was assumed with a Young’s Modulus (E) of 2.8 MPa based on experimental data (Claiborne et al, 2013b). Monitoring of the computed maximum deformations on the FSI model confirmed the validity of this assumption.…”

“…The probability density function (PDF) of the SA was calculated for the whole domain. The PDF represents the potential of a large population of platelets flowing past the PHV to activate according their corresponding distribution in the SA domain, and thus can be referred to as the “thrombogenic footprint” of a cardiovascular device (Alemu et al, 2010; Claiborne et al, 2013b; Xenos et al, 2010). …”

“…The commissural ROIs were chosen because they are exposed to higher SA levels relative to the reference core flow ROI, and therefore they have higher potential to activate platelets (Alemu et al, 2010; Bluestein et al, 1997). A single platelet trajectory related to the most frequently occurring SA value (mode) was selected for each ROI (Claiborne et al, 2013b). These four representative stress-time loading waveforms were programmed into a computer-controlled hemodynamic shearing device (HSD) for in vitro platelet activation measurement (Xenos et al, 2010).…”

“…We previously applied this methodology to optimize various cardiovascular devices, such as ventricular assist devices (Chiu et al, 2013), MHVs (Alemu et al, 2010; Nobili et al, 2008a; Xenos et al, 2010), and for the first-stage optimization of a trileaflet PHV prototype (Claiborne et al, 2013b). In the latter study, the thrombogenic potential of the valve was assessed with the valve either in the fully open position during forward flow or with the valve closed during regurgitation.…”

“…In this study, the PHV that was tested was a surgical version of the polymer valve that has been developed in Stony Brook University (Claiborne et al, 2013b) and is being commercialized by Polynova Cardiovascular Inc. (Stony Brook, NY, USA). The FSI approach was employed for the full cardiac cycle to obtain a more reliable solution of the fluid shear stresses and the thrombogenic potential.…”